Cell Division (Lecture 1) Flashcards

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1
Q

What is cell division?

A

The process by which cells make more cells

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2
Q

Why does cell division occur?

A

– Growth – Cell replacement – Healing – Reproduction

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3
Q

Cell division occurs by…

A
  1. Mitosis (eg, hair stem cells) 2. Meiosis (germ or sex cells)
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4
Q

If a stem cell divides once a day for 75 years how many times would it have divided without making a mistake?

A

Over 27,000

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5
Q

What are the main stages of the cell cycle?

A
  1. G1 phase 2. S phase 3. G2 phase 4. M phase 5. G0 phase
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6
Q

What happens in the G1 phase (gap 1)?

A

Growth, cellular metabolism

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7
Q

What happens in S phase (Synthesis)?

A

DNA replication (chromosome duplication)

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8
Q

What happens in G2 phase (Gap 2)?

A

Preparation for mitosis

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9
Q

What happens in M Phase (mitosis)?

A

Chromosomal separation and cytokinesis

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10
Q

Which parts of the cell cycle are involved in interphase?

A
  1. G1 phase 2. S phase 3. G2 phase 4. G0 phase
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11
Q

Interphase is the time between…

A

Successive mitoses G1 + S + G2

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12
Q

Cells exit the cell cycle from G1 and enter a state called… and why?

A

G0, Cells that are not actively cycling may exit

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13
Q

Cells that enter the G0 state are said to be…

A

Quiescent

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14
Q

What would be considered quiescent with respect to the cell cycle?

A

A neutron with its axon and dendrites would be quiescent with respect to the cell cycle. It will not re-enter the cell cycle

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15
Q

What are homologous chromosomes?

A

Homologous chromosomes are two pieces of DNA within a diploid organism which carry the same genes, one from each parental source

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16
Q

What is a centromere?

A

The centromere is the specialized DNA sequence of a chromosome that links a pair of sister chromatids

17
Q

After two homologous chromosomes undergo S phase what happens?

A

Each chromosome duplicates creating sister chromatids attached to one centromere

18
Q

What are sister chromatids?

A

A sister chromatid refers to the identical copies (chromatids) formed by the DNA replication of a chromosome, with both copies joined together by a common centromere

19
Q

What events occur in Prophase?

A

Chromosomes condense. Centrosomes radiate microtubules and migrate to opposite poles

20
Q

What are chromatin fibres?

A

Chromatin is composed of DNA and histones that are packaged into thin, stringy fibers

21
Q

What is a nuclear envelope?

A

The double-layered membrane enclosing the nucleus of a eukaryotic cell. The nuclear envelope has pores that allow the passage of materials into and out of the nucleus. Also called nuclear membrane.

22
Q

What events occur in Prometaphase?

A

Microtubules of the mitotic spindle attach to chromosomes, nuclear envelope starts to break down

23
Q

What are kinetochores?

A

A complex of proteins associated with the centromere of a chromosome during cell division, to which the microtubules of the spindle attach

24
Q

What events occur in Metaphase?

A

Chromosomes align in center of cell

25
Q

What events occur in Anaphase?

A

Sister chromatids (which become individual chromosomes when the centromere splits) separate and travel to opposite poles

26
Q

What events occur in Telophase?

A

Nuclear envelope re-forms and chromosomes decondense

27
Q

What are ploidy levels?

A

The number of complete sets of chromosomes in a cell

28
Q

What is a cell with a complete set of chromosomes?

A

Haploid

29
Q

Sperm cell or an egg cell would be an example of what cell?

A

Haploid cell

30
Q

What would a diploid cell have?

A

A diploid cell would have two complete sets of chromosomes. One copy from the mother and one copy from the father

31
Q

What are examples of diploid cells?

A

Example of a diploid cell would be a somatic cell, such as a leaf cell or a skin cell or a stem cell in your colon

32
Q

Explain haploid (n) vs diploid (2n)

A

When one unique chromosome from Dad’s germ cell (haploid cell (n)) comes together with 1 unique chromosome from Mom’s germ cell (haploid (n)) it creates one homolog (homologous chromosomes) which are now diploid cells (2n). 2 unique chromosomes (2n).

33
Q

What happens to diploid somatic cells after s phase?

A

Still considered a diploid cell, even though there are 4 complete sets of chromosomes. This is a short and transient phase. Note that the amount of DNA has doubled.

34
Q

What events occur in cytokinesis (animal)?

A

Cytokinesis divides the cytoplasm of a parental cell into two genetically identical daughter cells

35
Q

What types of cells does Mitosis occur in?

A

Stem cells

36
Q

Amount of ______ changes, but NOT the ________ level in Mitosis

A

Amount of DNA changes, but NOT the ploidy level in Mitosis